Bad respawn bug shown here. You can (sometimes) run into a random fall boundary when exiting from the first tunnel being close to the walls, respawning you far behind where you fell. If you fall off the bridge, the lack of any respawn point here will get you to make your own way to get back to the track. The fall boundaries and the respawn points needs to be checked out. Questionable item routes.

Bad sectioning of item/enemy routes #1 and #2 (zero-based numbering). This trivial route split was supposed to end on the first ramp; but instead, both routes persist redundantly for a while, and end up dependently taking different routes on the next important junction where you either turn 90° or go straight. Thus, Bullet Bill may fail there if you use it after entering the "wrong" route (depending on the route you took earlier; reset after a respawn).